Window not repainted, when open many windows

I run application 6 times (6 open windows). Application is in attachment.
Then I successively maximize windows.
Fifth window (and all next) not repaints. Title of window appears on top. But content not paints.
Sequence number of window with error is not constant.

Error:
I put stack trace to file error.log

When I run Ensemble 4 times, fourth window not repaints.